In packaging applications involving garbage bags and food storage bags, the bags are often connected in series by perforations and wound about a dispensing roll. To remove a leading bag from the dispensing roll, one unwinds the bag from the dispensing roll and breaks the perforation connecting the bag to the adjacent bag on the roll.
Since removing bags in the foregoing manner can be a difficult task, automated techniques have been developed for breaking the perforations between adjacent bags prior to winding the bags about a dispensing roll. To remove a bag from the dispensing roll, the bag is simply unwound from the roll. In one such automated technique, a series of bags connected by perforations are fed by feed rollers through a festooner and to a conveyor. The conveyor operates at a slower speed than the feed rollers. The festooner is driven with a low clutch, a high clutch, and a brake that are mechanically connected by an assembly of belts and pulleys. The festooner operates at three different speeds, depending upon the position of a bag passing through the festooner. First, the festooner operates at a slow speed to take up slack generated in a bag as it passes into the conveyor. After the slack in the bag is taken up, the festooner operates at a relatively high speed to "snap" the perforation between the trailing edge of the bag and the leading edge of the next adjacent bag prior to passage of the trailing edge of the bag through the festooner. After the perforation is snapped, the festooner is stopped by a brake so that it is in a position to receive the now disconnected leading edge of the adjacent bag. Once the leading edge of the adjacent bag passes through the festooner and into the conveyor, the foregoing process for breaking the perforation at the trailing edge of this adjacent bag is repeated.
The foregoing technique is disadvantageous because it fails to adequately control the bags as the perforations therebetween are broken. For example, by "snapping" the perforations between two bags while the festooner is rotating at high speeds and then suddenly stopping festooner rotation, there is minimal positive control over the trailing portion of the lead bag and the leading portion of the adjacent trailing bag. This can cause the trailing portion of the lead bag to swing out of control ahead of the remainder of the lead bag and get improperly entangled in the conveyor. Similarly, this "snapping" action can cause the leading portion of the trailing bag to swing backward and get entangled about the feed rollers.
Another drawback of the foregoing technique is that using high speed rotation to snap perforations can lead to inconsistent perforation breaks. If the perforation break is made either too quickly or in the wrong location, the leading edge of the trailing bag becomes skewed. This skewed leading edge can then become entangled in the festooner. Also, when the bags are later wound on a dispensing roll, the skewed edge may not properly align with the other bags on the roll.
A need therefore exists for a method and apparatus for breaking film perforations which overcomes the above-noted drawbacks associated with the foregoing technique.